(a) Field of the Invention
This invention relates to improvements in electric shutters for cameras.
(b) Description of the Prior Art
Generally an electric shutter for cameras is so arranged that, by a shutter releasing operation, a shutter opening driving member may be started to begin an exposure and, when a proper exposure time has elapsed, an electromagnetic device may work to start a shutter closing driving member to complete the exposure. Now, in the conventional electric shutter, in case the current source voltage drops to be below a predetermined level due to the consumption of the current source battery or no electric current flows at all to the electromagnetic device due to any cause, even if the proper exposure time elapses, the electromagnetic device will not be excited well or at all and therefore the shutter will remain open. Therefore, in such case, until the current source battery is replaced with a new one or the trouble is remedied, not only the next photographing but also the rewinding of the film will be able to be made, much to the disadvantage. In order to eliminate such defect, there is already suggested an automatic switching system wherein, when the voltage of the current source battery drops to be below a predetermined value, after the lapse of a fixed exposure time determined only by a mechanical means, the shutter will be closed. However, such system has defects that the mechanism is complicated and that the cost is high.